Chapter 1, 16, and 25 of Medical Physiology (Guyton ) 생리학총론 5 체액생리 Chapter 1, 16, and 25 of Medical Physiology (Guyton ) 김영미 (ykpak@khu.ac.kr) 경희대학교 의과대학 생리학교실 Tel: 02-961-0908

생리학 학습목표 (2013) We discuss body fluid volume (체액평형) 세포막을 통한 물의 이동량에 영향을 끼치는 인자들에 대해 설명한다 삼투현상의 원리를 이해하고 반트 호프(van't Hoff) 공식을 기술한다. 삼투질 농도 변화 시 변화하였던 세포의 용적이 다시 본래의 용적으로 되돌아가는 기전에 대해 설명한다 도난(Donnan) 평형을 기술한다. 모세혈관에서의 물질 이동을 스탈링(Starling)의 가설로 설명한다. (순환계에서) We discuss body fluid volume (체액평형) constituents of the extracellular fluid (전해질평형) acid-base balance (산염기평형) The control of fluid exchange between extracellular and intracellular compartments.

Do you know the difference? Equilibrium Steady state Homeostasis 산-염기 평형, 삼투압 Central Dogma: DNA->RNA-> proteins 체온, pH, 섭식조절

Control Systems of the Body Homeostasis: maintenance of nearly constant conditions in the internal environment Examples of control mechanisms within organs Regulation of O2 and CO2 concentrations in the ECF O2-buffering function of hemoglobin Regulation of arterial blood pressure Baroreceptor system Baroreceptros: In the wall of the bifurcation region of the carotid arteries in the neck In the arch of the aorta in the thorax Vasomoter center

Characteristics of Control Systems Negative Feedback positive Feedback Negative Feedback Most control system of the body “Gain” of a control system Positive Feedback Cause vicious cycles and death Useful systems blood clotting cascade Child birth Generation of nerve signals Adaptive control Most complex type of control Interconnected control Feed-forward control Delayed negative control

Control system to maintain homeostasis Negative feedback Carotid artery baroreceptor Diastolic/systolic

Balance between fluid intake and output during steady-state conditions 체액평형 = 수분평형 Water: The most abundant component of human body Ideal media for living phenomena. Universal solvent of organic and inorganic substances Vehicle of transport for all solute and gases 물의 이동과 체액 항상성 유지 섭취와 배설의 균형 섭취: 음료와 음식 + 대사수 배설: 소변 + insensible Extensive burn: 10-fold increase of insensible water loss Heavy exercise: fluid loss in sweat Diarrhea: water loss in feces

Body fluid: ECF and ICF resting membrane potential (160 ~-80 mv) Na+ vs. K+ 불균일한 분포 resting membrane potential (160 ~-80 mv) 세포내외에 전기적 구배를 형성 신경의 흥분전달 외분비선 (땀샘, 소화선)에서 체액분비의 구동력 이 세포내외의 ion 농도 차이를 유지하는 것이 생체의 기능유지, 즉 살아 있다는 것임 Kyung Hee University

Definition: Body Fluids (체액) 성인체중의 60% 차지하는 수용액으로 ions 과 여러 물질이 녹아 있음 노화에 따라 체액은 감소 지방이 많아도 체액 감소 (Female<male, metabolic syndrome pt.<normal) Intracellular fluid (ICF, 새포내액): fluid inside the cells = 2/3 of total fluid (~40% of BW) Extracellular fluid (ECF, 세포외액): fluid outside the cells = 1/3 of total fluid (~20% of BW) 분포하는 장소에 따라 혈장, 간질액, 림프액, 뇌척수액 등이 있다.. Blood plasma (혈장) (~4%) (serum 과의 차이?) Interstitial fluid (간질액)(~16%): the fluid in the interstitium Lymph fluid: fluid from interstitial space into blood to carry proteins and large molecules Transcellular fluid (세포 삼출액): total body water contained within epithelial lined spaces Cerebrospinal fluid (CSF), Bladder urine, synovial, peritoneal, pericardial, and intraocular fluid, other?? Its composition may differ markedly from that of the plasma or interstitial fluid ECF Vs. ICF More Na+, Cl-, HCO3-, nutrients (oxygen, glucose, fatty acids, amino acids) than ICF More K+, Mg2+, PO4- than ECF

Normal Ranges and Physical Characteristics of Important ECF Constituents Determination factors For life or death? Body temp. pH K+

Blood BLOOD volume (~7% of BW, 5L) = Plasma (ECF, ~60% of blood, ~3L)+ Intracellular of RBC (ICF) Plasma (with anti-coagulant) vs Serum (without anti-coagulant) Hematocrit (packed red cell volume) Normal range: 0.4 for male, 0.36 for female anemia (빈혈, ~0.1) vs. polycythemia (적혈구증가증, ~0.65) Kidney

Body fluid compartments (체액 구획) 40% ~16% ~4% 20% Example: 70kg person Transcellular fluid = 1~2L

The Indicator-Dilution Principle Measurement of Fluid Volumes in the Different Body Fluid Compartments 체액의 구분에만 분포하는 지시물질(Z)을 사용하는 방법으로 아는 양의 X를 투여하고 X가 균등히 분포할 때까지 기다린 후 측정 하고자 하는 부분의 체액을 뽑아 X의 농도를 잰다 체액구분의 용적 V=A/C 만일 배설되는 물질이면, V=(A-E)/C V: 체액구분의 부피. A: 투여한 지시물질의 양, C: 해당 체액구분 내의 지시물질의 농도 E: 배설된 양

희석법 (dilution method) 으로 체액량을 측정 시 지시물질이 갖추어야 할 조건 지시물질의 측정하고자 하는 구분 안에서만 확산하고 그 안에 균등히 분포하여야 한다. 독성이 없고 체내에서 대사되거나 합성되지 않아야 한다. 쉽게 배설되는 것이라면 배설된 양을 정확히 알 수 있어야 한다. 이 때는 : V=(A-E)/C의 식으로 보정하며 여기에서 E는 배설된 양이다. 4) 쉽게 채취하여 그 농도를 쉽게 측정할 수 있어야 한다.

체액구획 측정에 사용되는 물질과 그 물리적 특징 및 계산방법 총수분량: 체액의 모든 구분에 균등하게 녹아 들어가는 중수(D2O), 삼중수(T2O)또는 antipyrine 등을 사용 세포외액량: 모세혈관 벽은 쉽게 통과하나 세포막은 통과하지 않는 물질을 택해야 하는데 이를 위한 이상적인 물질이 없다. 22Na, 125I-iothalamate, thiosulfate등의 동위원소, 대사되지 않는 당류인 이눌린, 만니톨 등을 사용. 세포내액량 (ICF) 과 세포간질액량 (interstitial fluid): 직접 측정 못함 세포내액량 = 총수분량-세포외액량 세포간질액량 = 세포외액량 - 혈장량 혈장량 (Plasma): 모세혈관 벽을 통과하지 못하는 지시물질을 사용, 동위원소로 표시한 알부민이나 Evans blue dye (=T-1824, 혈장알부민과 쉽게 결합해 혈관 밖으로 나가지 못함) 등을 사용 Blood volume는 51Cr로 표시한 적혈구를 사용하거나 hematocrit으로부터 계산.

Structure of the interstitium 1/6 of total body volume Two solid structures Collagen fiber bundles (long) Proteoglycan filaments (thin): hyaluronic acid (98%) + protein (2%) Interstitial fluid (간질액) Derived by filtration and diffusion from the capillary Constituents are almost same as plasma, but low proteins Entrapped mainly in the minute space among the proteoglycan filament -> tissue gel (99% of interstitial fluid) Not flow but diffuse for transport Small free fluid vesicles in interstitium (<1%) Edema: tremendous increase of free fluid

Structure of the microcirculation and capillary system Exchange of water, nutrients, and other substances between the blood and interstitial fluid: Diffusion through capillary membrane Structure of the capillary wall Structure of the mesenteric capillary bed Capillary: a unicellular endothelial cell (EC) layer surrounded by a very thin basement membrane Total thickness of the capillary wall = 0.5 μm Internal diameter = 4-9 μm (barely large enough for RBC) “Pores” in the capillary membrane intercellular cleft (6-7 nm) (smaller than albumin protein) Plasmalemmal vesicles -> form vesicular channels on EC

Special types of pores occur in the capillaries of certain organs Brain: tight junction of endothelial cells blood brain barrier Allow only extremely small molecules (water, O2, CO2, etc) to pass Liver: wide open clefts between endothelial cells Pass almost all dissolved substances Gastrointestinal capillary membrane Midway between those of the muscle and those of the liver Glomerular tufts of the kidney Numerous fenestrae (small oval windows through EC) allow to filter tremendous amounts of very small molecules and ionic substances, but not proteins through glomeruli without passing clefts of EC (A) Diagram of a brain capillary in cross section and reconstructed views, showing endothelial tight junctions and the investment of the capillary by astrocytic end feet. (B) Electron micrograph of boxed area in (A), showing the appearance of tight junctions between neighboring endothelial cells (arrows). (A after Goldstein, Goldstein and Betz, 1986; B from Peters et al., 1991.) Arrows: Tight junctions Blood Brain Barrier (BBB)

Constituents of ECF and ICF (1) Ionic composition Non-electrolytes of the plasma

Constituents of ECF and ICF (2) The composition of ECF is carefully regulated by various mechanisms by kidney. The cells are exposed to the fluid that contains the proper concentrations of electrolytes, nutrients, and toxic materials. ICF Separated from ECF by cell membrane See Fig. 25-2, Table 25-2 A large amount of protein ECF = plasma + interstitial fluid They are similar because they are separated by highly permeable capillary membrane Protein concentrations : plasma >> interstitial spaces (because of small capillary membrane permeability) Because of Donnan effect, slightly higher concentration (ca 2%) of cation in plasma than interstitial fluid

Donnan effect (Gibbs-Donnan effect) on equilibrium between semi-permeable membrane Interstitial Plasma Because of the presence of different charged impermeable substance like the negative charged proteins, the behavior of charged particles near a semi-permeable membrane to sometimes fail to distribute evenly across the two sides of the membrane

Constituents of Extracellular and Intracellular Fluids (3) Effect of Donnan equilibrium

Fluid filtration across capillaries Determination factors Hydrostatic pressure By water (highly permeable) Osmotic pressures By small solutes like Na+, Cl-, other electrolytes (impermeable) Capillary filtration coefficient ICU 환자에서 가장 흔한 문제: body fluid 를 각 구획에서 적절하게 유지하지 못함

Basic Principles of Osmosis and Osmotic Pressure Relation between moles and osmoles Solute 의 정확한 농도에 상관없이 용액중에 녹아 있는 solute particle의 숫자를 표기 하기 위해 osmole 을 도입 1 osmole (osm) = 1 mole (6.23x1023) of solute particle Example: 1 mole glucose = 1 osmole 1 mole NaCl = 2 osmole (Na+ + Cl-) 1 mole Na2SO4 = 3 osmole (2Na+ + SO4-) 1mOsm = 10-3 Osm Osmolality vs. Osmolarity Osmolality = osmoles per kilogram of water Osmolarity = osmoles per liter of solution Capillary: semi-permeable membrane Structure of the capillary wall

삼투압 (Osmotic Pressure) (osmolality) E C2 PV nR -1 E=mC2 M I T PV=nRT MIT Open course

Basic principles of Osmosis and Osmotic pressure Osmosis: net diffusion of water caused by a concentration difference of water Osmotic pressure: The exact amount of pressure required to stop osmosis of the solution Osmotic pressure (p) calculation: van’t Hoff’s law p = CRT C: the molar solute concentration (Osm/L) R: ideal gas constant (62.36367 LmmHgK-1mol-1) T: absolute temperature (oK) 1mOsm/L => 19.3 mmHg/mOsm/L at 37oC Since the total body fluid has 300 mOsm, p of the body fluid = 300 x 19.3 mmHg = 5790 mmHg But the measured value is 5500 mmHg (because, ions are attracted to one another, actual osmotic pressure of the body fluid is about 0.93 times the calculated value.) Osmotic pressure pV=nRT -> p=(n/V) x RT

Calculate osmotic pressure of saline solution 0.9% NaCl = 0.9g NaCl /100ml = 9 g/L mw of NaCl = 58.5 g/mol Molarity of 0.9% NaCl = 9 (g/L)/58.5 (g/mol) = 0.154 mol/L = 0.154 x 2 Osm/L = 0.308 Osm/L Can you calculate osmotic pressure? the potential p=308mOsm/L x 19.3 mmHg/mOsm/L = 5944 mmHg Osmotic coefficient of NaCl = 0.93 the actual osmolarity = 308x0.93 = 286 mOsm/L the actual p=286mOsm/L x 19.3 mmHg/mOsm/L = 5519 mmHg Contributors of osmolarity in ECF: Na+ and Cl- Contributors of osmolarity in ICF: K+ and the remainders

Constituents of ECF and ICF (3)

Osmotic Equilibrium is maintained between ICF and ECF Isotonic solution: A solution have same osmolarity with the cell Usually 282 mOsm/L or 0.9% of NaCl solution Hypotonic solution: A solution have lower osmolarity than cell Hypertonic solution: A solution have lower osmolarity than cell

Volume and Osmolality of Extracellular and Intracellular Fluids in Abnormal States Remember! Water moves rapidly across cell membranes; therefore, the osmolarities of intracellular and extracellular fluids remain almost exactly equal to each other except for a few minutes after a change in one of the compartments. Cell membranes are almost completely impermeable to many solutes; therefore, the number of osmoles in the extracellular or intracellular fluid generally remains constant unless solutes are added to or lost from the extracellular compartment.

Effect of adding saline solution to extracellular solution Isotonic Hypotonic Hypertonic

Calculation of fluid shift and Osmolarities after infusion of hypertonic saline If 2L of 3.0% saline (0.513 M/L = 2051 mOsm) are infused to 70 kg patient whose initial plasma osmolarities is 280 mOsm/L, what would be the intracellular and extracellular fluid volumes and osmolarities after osmotic equilibrium?

모세혈관에서 물질, 수분의 교환 p172 Capillary microcirculation CNS, 폐, 골격근 등 신장, 소화관, 내분비선 등 비장, 간, 골수 등 Blood Brain Barrier

Exchange of fluid molecules Average rate of blood flow Average capillary pressure Average rate of transfer of substances Diffusion through the capillary membrane because of thermal motion of water and dissolved substances Lipid-soluble substances Through the cell membrane Water-soluble, non-lipid soluble substances Ions, glucose Through the pores Net diffusion rate depends on Molecular size Concentration difference Membrane permeability

The permeability of capillary pores depends on the molecular diameters of substances

Starling equation 세동맥과 세정맥의 F 값은? Net Filtration Pressure Hydrostatic   세동맥과 세정맥의 F 값은? Hydrostatic pressure Osmotic 여과 vs. 재흡수 Net Filtration Pressure

Fluid pressure and colloid osmotic pressure operate capillary membrane Four Primary Hydrostatic and Colloid Osmotic Forces Determine Fluid Movement Through the Capillary Membrane The capillary pressure (Pc), which tends to force fluid outward through the capillary membrane. The interstitial fluid pressure (Pif), which tends to force fluid inward through the capillary membrane when Pif is positive but outward when Pif is negative. The capillary plasma colloid osmotic pressure (Pp), which tends to cause osmosis of fluid inward through the capillary membrane. The interstitial fluid colloid osmotic pressure (Pif), which tends to cause osmosis of fluid outward through the capillary membrane. NFP=(Pc-Pif) - (Pp- Pif) Net filtration pressure (NFP): net fluid filtration across the capillaries

Four Primary Hydrostatic and Colloid Osmotic Forces Capillary pressure (Pc) Direct measurement by micropipette cannulation: Atrial end =30-40 mmHg venous end = 10-15 mmHg average = 25 mmHg Indirect measurement (isogravimetric) = functional =17 mmHg Interstitial fluid pressure (Pif) : In tightly encased tissues (brain, kidney, eye): positive value different between inside and outside CSF = +10 mmHg vs brain interstitial fluid pressure = +4 to +6 mmHg Kidney capsule pressure = +13 mmHg vs renal interstitial fluid pressure = +6 mmHg In loose subcutaneous tissue: negative value Lymphatic system: a slight negative pressure

Four Primary Hydrostatic and Colloid Osmotic Forces III. Capillary plasma colloid osmotic pressure (Pp) Proteins in the plasma (albumin, globulin, fibrinogen, etc) -> 19 mmHg Donnan effects caused by cations -> 9 mmHg IV. Interstitial fluid colloid osmotic pressure (Pif) Due to the leak of small amount of plasma proteins into the interstitial spaces, protein concentration of interstitial fluid is 40% of that in the plasma = 3 g/dl -> 8 mm Hg Albumin is important !! mw 69,000 140,000 400,000

Starling Equilibrium NFP=(Pc-Pif) - (Pp- Pif) Under normal conditions, a state of near-equilibrium exists at the capillary membrane: the amount of fluid filtering outward from the arterial ends of capillaries = almost exactly the fluid returned to the circulation by absorption. (average of atrial and venous ends) The normal rate of net filtration in the entire body = 2 mL/min Thus, 1mmHg imbalance causes 6.67 mL/min Kf = capillary filtration coefficient (capacity of capillary) Brain, muscle <subcutaneous tissue <intestine < liver, kidney Filtration = Kf x [(Pc – Pif )– (pc - pif)] NFP=(Pc-Pif) - (Pp- Pif) Starling equation illustrates the role of hydrostatic and oncotic forces (the so-called Starling forces) in the movement of fluid across capillary membranes.

Filtration vs. Reabsorption

Safety factors that prevent edema Safety factor caused by low compliance of the interstitium in the negative pressure range: 간질의 압력이 약간 변화 하더라도 간질액의 용적이 거의 변하지 않는다. 3 mmHg Importance of interstitial gel in preventing fluid accumulation in the interstitium: Interstititial free fluid pressure가 음압인 경우 간질액이 Gel 상태 이어서 간질액의 축적을 막는다-반대로 양압으로 바뀌면 체액이 축적된다. Importance of the proteoglycan filaments as a “Spacer” for the cells and in preventing rapid flow of fluid in the tissues: 간질의 Proteoglycan filament가 spacer로 작용하여 유체의 흐름을 방지한다. Increased lymph flow as a safety factor against edema: 간질액 압이 증가하면 Lymph의 흐름이 급격히 (10-50배) 증가하여 부종에 대한 안전장치로 역할을 한다. 7 mmHg “Washdown” of the Interstitial Fluid Protein as a Safety Factor Against Edema: 7 mmHg lymph 흐름이 증가하면 간질액내 단백질 농도 감소, but 단백질은 모세혈관 통과 못하므로 lymph 액 내 존재 -> interstitial fluid colloid osmotic pressure -> lower the net filtration forces -> prevent fluid accumulation

Fluid in “potential space” of the body Potential spaces: abdominal cavity (복강), pleural cavity (흉강), pericardial cavity (심낭), synovial cavity (joint cavity and bursae, 관절강) Fluid is exchanged between the capillaries and the potential spaces. Lymphatic vessels drain protein from the potential spaces. Removal of proteins through lymphatics or other channels and returned to the circulation Edema fluid in the potential spaces is called “Effusion.” Effusion (삼출액): edema fluid collected in the potential space Ascite (복수): effusion fluid collected in the abdominal cavity

Clinical abnormalities of fluid volume regulation Hyponatremia < 142 mEq/L < Hypernatremia Causes of hyponatrinemia: Excess water or loss of sodium Diarrhea and vomiting, Overuse of diuretics Addison’s disease (decreased secretion of aldosterone) > hypo-osmotic dehydration > decrease of ECF volume 3) Excess water retention by excessive secretion of antidiuretic hormone (ADH) -> hypo-osmotic overhydration -> increase of ECF volume Causes of hypernatrinemia: Water loss or excess sodium Decrease of ADH (diabetes insipitus) or no response to ADH (nephrogenic diabetes insipitus) > hyper-osmotic dehydration > decrease of ECF volume 2) excessive secretion of the sodium-retaining hormone aldosterone -> hyper-osmotic overhydration

Edema: excess fluid in the tissue (Edema is an observable swelling from fluid accumulation in certain body tissues) Intracellular Edema: 1) depression of metabolism 2) lack of nutrition or inflammation Extracellular edema Abnormal leakage of fluid from the plasma to the interstitial spaces across the capillaries: Filtration = Kf x (Pc – Pif – pc + pif) increase capillary filtration coefficient increase capillary hydrostatic pressure Decrease plasma colloid osmotic pressure Lymphatic blockage to return from interstitium into the blood Infection by filaria nematode Cancer after surgery (removal of lymph vessels)